1. Field of the Invention
This application is a national state entry of PCT/GB99/03891 filed Nov. 23, 1999, which claims priority from British application 9825644.9 filed Nov. 23, 1998.
The present invention generally relates to a cipher and in particular to a cipher in which the secret cipher code which is required for both enciphering and deciphering is information which describes the process used to carry out enciphering.
2. Related Art
Two commonly used types of cryptographic algorithms are private key algorithms which use a single shared key and public key algorithms which use two keys: a public key and a private key.
In these prior art algorithms the encryption process used is fixed although the particular encryption process can be selectable by user e.g. by using a particular encryption program (algorithm). The security of the encryption is provided by the key which is secretly exchanged between the encrypter operator and decrypter operator. Such currently implemented ciphers are not easily scalable since they are defined for a specific block size and key size. In many instances the key is not big enough e.g. many ciphers have only 64 bit keys.